U.S. patent application number 13/904813 was filed with the patent office on 2013-12-05 for methods and apparatus for treating a hydrocarbon stream.
The applicant listed for this patent is UOP LLC. Invention is credited to Adam Gross, Deng-Yang Jan, Wugeng Liang, Mark G. Riley.
Application Number | 20130323134 13/904813 |
Document ID | / |
Family ID | 49670503 |
Filed Date | 2013-12-05 |
United States Patent
Application |
20130323134 |
Kind Code |
A1 |
Riley; Mark G. ; et
al. |
December 5, 2013 |
Methods and Apparatus for Treating a Hydrocarbon Stream
Abstract
Disclosed is an apparatus for removing water, nitrogen
compounds, and unsaturated aliphatic compounds from a hydrocarbon
feed stream including a water removal zone, a nitrogen removal
zone, and an unsaturated aliphatic compound removal zone. By on
aspect, the water removal zone includes a water selective
adsorbent, the nitrogen removal zone includes a nitrogen selective
adsorbent, and the unsaturated aliphatic compound removal zone
includes an unsaturated aliphatic compound removal material.
Inventors: |
Riley; Mark G.; (Hinsdale,
IL) ; Liang; Wugeng; (Elgin, IL) ; Jan;
Deng-Yang; (Elk Grove Village, IL) ; Gross; Adam;
(Glencoe, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Family ID: |
49670503 |
Appl. No.: |
13/904813 |
Filed: |
May 29, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61653789 |
May 31, 2012 |
|
|
|
Current U.S.
Class: |
422/187 ;
210/252; 210/263 |
Current CPC
Class: |
B01J 20/2808 20130101;
B01D 15/26 20130101; B01J 20/165 20130101; C07C 7/005 20130101;
C07C 7/005 20130101; B01D 15/00 20130101; B01J 20/18 20130101; B01J
8/00 20130101; C07C 7/13 20130101; C07C 7/13 20130101; C07C 15/04
20130101; C07C 15/04 20130101 |
Class at
Publication: |
422/187 ;
210/252; 210/263 |
International
Class: |
B01D 15/26 20060101
B01D015/26; B01J 8/00 20060101 B01J008/00 |
Claims
1. An apparatus for treating a hydrocarbon feed stream comprising
an aromatic compound, a nitrogen compound, water, and an
unsaturated aliphatic compound, the apparatus comprising: a water
removal zone having a water removal device configured to remove at
least a portion of the water from the feed stream as it flows
through the water removal zone; a nitrogen removal zone in fluid
communication with the water removal zone having a nitrogen
selective adsorbent configured to contact the feed stream as it
flows through the nitrogen removal zone to remove a nitrogen
compound from the feed stream; and an unsaturated aliphatic
compound removal zone in fluid communication with the nitrogen
removal zone having an unsaturated aliphatic compound removal
material configured to contact the feed stream as it flows through
the unsaturated aliphatic compound removal zone to remove an
unsaturated aliphatic compound from the feed stream to produce a
treated feed stream.
2. The apparatus of claim 1, wherein the aromatic hydrocarbon
comprises benzene; and an ethylbenzene production zone in fluid
communication with the unsaturated aliphatic compound removal zone
having an ethylbenzene production catalyst configured to contact
the treated feed stream as it flows through the ethylbenzene
production zone and to convert at least a portion of the benzene in
the treated feed stream to ethylbenzene.
3. The apparatus of claim 1, further comprising a styrene monomer
production zone for receiving an ethylbenzene stream and converting
at least a portion of the ethylbenzene to styrene; an inhibitor
source in fluid communication with the styrene monomer production
zone for supplying an inhibitor including an inhibitor nitrogen
compound for restricting polymerization and/or corrosion of
equipment within the styrene monomer production zone; a benzene
separation zone for separating a benzene recycle stream including
benzene and the one or a different nitrogen compound from a styrene
stream; and a recycle line for passing the benzene recycle stream
to the water removal zone inlet to provide at least a portion of
the hydrocarbon feed stream to the water removal zone inlet.
4. The apparatus of claim 1, wherein the water removal device
includes a water removal vessel housing a water selective adsorbent
configured to contact the hydrocarbon feed stream as the feed
stream passes through the water removal vessel.
5. The apparatus of claim 4, wherein the water selective adsorbent
comprises a zeolite having a about a 2 .ANG. to about an 8 .ANG.
pore volume for selectively adsorbing water from the hydrocarbon
feed stream.
6. The apparatus of claim 5, wherein the water selective adsorbent
comprises a zeolite selected from the group consisting of zeolite
A, zeolite X, and zeolite Y.
7. The apparatus of claim 6, wherein the zeolite has a pore
diameter of between about 2 .ANG. and about 5 .ANG. and comprises
zeolite A.
8. The apparatus of claim 1, wherein the nitrogen selective
adsorbent includes a basic zeolite for removing at least a portion
of the nitrogen compounds from the feed stream.
9. The apparatus of claim 8, wherein the basic zeolite has a Si/Al
ratio of between about 1 and about 12.
10. The apparatus of claim 1, wherein the unsaturated aliphatic
compound comprises a diene and the unsaturated aliphatic removal
material comprises a material selected from the group consisting of
acidic clay, acidic zeolite and sulfate supported metal oxides.
11. The apparatus of claim 4, wherein the water removal zone, the
nitrogen removal zone, and the unsaturated aliphatic compound
removal zone each includes a vessel for holding the respective
water selective adsorbent, nitrogen selective adsorbent, and
unsaturated aliphatic removal material.
12. The apparatus of claim 4, wherein the water selective
adsorbent, nitrogen selective adsorbent, and unsaturated aliphatic
removal material are all housed within a single vessel.
13. An apparatus for producing styrene, the apparatus comprising:
an ethylbenzene production zone having an ethylbenzene production
catalyst configured to contact a feed stream including benzene to
convert at least a portion of the benzene in the feed stream to
ethylbenzene to form an ethylbenzene intermediate stream; a styrene
monomer production zone in fluid communication with the
ethylbenzene production zone and configured to receive at least a
portion of the ethylbenzene intermediate stream, and having a
styrene monomer production catalyst configured to contact the
ethylbenzene intermediate stream and to convert at least a portion
of the ethylbenzene in the ethylbenzene intermediate stream to
styrene to provide a styrene monomer intermediate stream including
at least styrene and benzene; an inhibitor source in fluid
communication with the styrene monomer production zone for
supplying an inhibitor including an inhibitor nitrogen compound for
restricting polymerization and/or corrosion of equipment within the
styrene monomer production zone; a separation zone for separating a
recycle benzene stream including the one or another nitrogen
compound from the styrene intermediate stream; a recycle line for
passing the benzene recycle stream to a treatment zone, the
treatment zone further comprising: a water removal zone configured
to remove at least a portion of the water from the feed stream as
it flows through the water removal zone; a nitrogen removal zone in
fluid communication with the water removal zone having a nitrogen
selective adsorbent configured to contact the feed stream as it
flows through the nitrogen removal zone to remove a nitrogen
compound from the feed stream; and an unsaturated aliphatic
compound removal zone in fluid communication with the nitrogen
removal zone having an unsaturated aliphatic compound removal
material configured to contact the feed stream as it flows through
the unsaturated aliphatic compound removal zone to remove an
unsaturated aliphatic compound from the feed stream to produce a
treated feed stream.
14. The apparatus of claim 13, wherein the water removal device
includes a water removal vessel housing a water selective adsorbent
configured to contact the hydrocarbon feed stream as the feed
stream passes through the water removal vessel.
15. The apparatus of claim 14, wherein the water selective
adsorbent comprises a zeolite having about a 2 .ANG. to about an 8
.ANG. pore diameter for selectively adsorbing water from the
hydrocarbon feed stream.
16. The apparatus of claim 15, wherein the water selective
adsorbent comprises a zeolite selected from the group consisting of
zeolite A, zeolite X, and zeolite Y.
17. The apparatus of claim 13, wherein the ethylbenzene production
zone includes at least one of an alkylation reactor and a
transalkylation reactor for converting at least a portion of the
benzene in the feed stream to ethylbenzene.
18. The apparatus of claim 13, wherein the nitrogen selective
adsorbent includes a basic zeolite for removing at least a portion
of the nitrogen compounds from the feed stream.
19. The apparatus of claim 14, wherein the basic zeolite has a
Si/Al ratio of between about 1 and about 12.
20. The apparatus of claim 13, wherein the unsaturated aliphatic
compound comprises a diene and the unsaturated aliphatic removal
material comprises a material selected from the group consisting of
acidic clay, acidic zeolite and sulfate supported metal oxides.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Application No.
61/653,789 which was filed on May 31, 2012.
FIELD OF THE INVENTION
[0002] This invention relates to methods and apparatus for treating
a hydrocarbon stream. More particularly, this invention relates to
methods and apparatus for treating a hydrocarbon stream including
an aromatic compound to remove water, nitrogen compounds, and
unsaturated aliphatic compounds from the stream.
BACKGROUND OF THE INVENTION
[0003] The alkylation or transalkylation of benzene with a C2 to
C20 olefin alkylating agent or a polyaklyl aromatic hydrocarbon
transalkylating agent is one of the primary sources for the
production of alkylbenzenes. For example, ethylbenzene is often
produced by the alkylation of benzene with ethylene. Ethylbenzene
may subsequently be used as a precursor for making styrene by the
dehydrogenation of the ethylbenzene. Often, the ethylbenzene and
styrene production facilities are integrated in an
ethylbenzene-styrene complex so that after the ethylbenzene is
produced it is sent to a downstream styrene plant that converts the
ethylbenzene into styrene through dehydrogenation. Styrene may in
turn be used to produce polystyrene, a widely used plastic, or
other products.
[0004] In an alkylbenzene production plant, benzene is fed along
with a C2 to C20 olefin alkylating agent or polyalklyaromatic
hydrocarbon transalklyating agent to an alkylation or
transalkylation reactor. Typically, benzene is fed along with
ethylene into an alkylation zone, including an alkylation reactor,
where alkylation of the benzene and ethylene over an alkylation
catalyst forms ethylbenzene. The ethylbenzene product stream
typically includes other components as well, such as
diethylbenzene. The stream may next be sent to a separation zone
where the ethylbenzene is separated from other components in the
stream to form a purified ethylbenzene stream.
[0005] In an ethylbenzene-styrene complex, the ethylbenzene is next
sent to a downstream styrene plant or section of the complex for
conversion of the ethylbenzene to styrene. According to one current
process, the ethylbenzene is sent to a dehydrogenation reactor
within the styrene plant, where a dehydrogenation reaction occurs
to form a mixed stream of styrene, benzene, and ethylbenzene. The
mixed stream is sent to an ethylbenzene-styrene splitter forming
separate ethylbenzene and styrene streams. An inhibitor is
typically added to the ethylbenzene-styrene splitter to restrict
polymerization of the styrene and corrosion within the splitter. In
many instances, the inhibitors include nitrogen compounds. The
ethylbenzene stream may be sent to an ethylbenzene recycle column
where an ethylbenzene recycle stream is separated from benzene and
toluene. The ethylbenzene may be recycled back to the
dehydrogenation reactor or reactors in order to produce additional
styrene. The benzene and toluene are typically sent to a
benzene-toluene splitter where the streams are separated and may be
sold.
[0006] Catalysts for aromatic conversion processes generally
comprise zeolitic molecular sieves. Examples include, zeolite beta
(U.S. Pat. No. 4,891,458); zeolite Y, zeolite omega and zeolite
beta (U.S. Pat. No. 5,030,786); X, Y, L, B, ZSM-5, MCM-22, MCM-36,
MCM-49, MCM-56 and Omega crystal types (U.S. Pat. No. 4,185,040);
X, Y, ultrastable Y, L, Omega, and mordenite zeolites (U.S. Pat.
No. 4,774,377); and UZM-8 zeolites (U.S. Pat. No. 6,756,030 and
U.S. Pat. No. 7,091,390). It is known in the art that the benzene
stream generated by the styrene zone includes contaminants, such as
nitrogen, unsaturated aliphatic compounds, and water such that it
has been undesirable to recycle the stream back to the alkylation
reactor to produce additional ethylbenzene. These contaminants,
even at ppm and ppb levels, can cumulatively act to poison the
aromatic conversion catalysts, such as aromatic alkylation
catalysts and significantly shorten their useful life. More
particularly, nitrogen compounds in the benzene stream, as well as
water and dienes or other unsaturated aliphatic compounds, are
known to deactivate the alkylation or transalkylation catalyst in
the alkylation zone and/or transalkylation zone adding additional
expense in having to change out or regenerate the catalyst. In
addition, due to the contaminants in this stream, the sale of this
benzene stream to third parties is generally below the typical
market value of benzene
[0007] A variety of guard beds having clay, zeolite, or resin
adsorbents to remove one or more types of nitrogen compounds and/or
other contaminants from an aromatic hydrocarbon stream upstream of
an aromatic conversion process are known in the art. Examples
include: U.S. Pat. No. 7,205,448; U.S. Pat. No. 7,744,828; U.S.
Pat. No. 6,297,417; U.S. Pat. No. 5,220,099; WO 00/35836; WO
01/07383; U.S. Pat. No. 4,846,962; U.S. Pat. No. 6,019,887; and
U.S. Pat. No. 6,107,535. An acidic molecular sieve H-Y has been
utilized to adsorb the nitrogen compounds from the stream.
[0008] It was previously identified that unsaturated aliphatic
hydrocarbons such as olefinic compounds, and particularly dienes,
can shorten the effective life of adsorbents, e.g. nitrogen
adsorptive adsorbents, used in the nitrogen removal guard beds that
are applied to various process streams, including aromatic
hydrocarbon feeds upstream of an aromatic conversion process such
as alkylation. These unsaturated aliphatic, e.g. olefinic,
compounds are present in aromatic process streams contaminated with
nitrogen compounds, including the benzene streams generated in
styrene process separation plants and other streams requiring
removal of the nitrogen compounds prior to being contacted with a
catalyst or other material susceptible to nitrogen poisoning. More
particularly, because dienes are typically present at
concentrations at least one order of magnitude greater than the
concentration of nitrogen compounds in the stream, and compete for
adsorbent sites in previous guard beds, they can greatly reduce the
capacity of the guard bed. Thus, attempts to simply increase the
size of the nitrogen guard bed have been largely ineffective.
[0009] Recent attempts, as described in U.S. patent application
Ser. Nos. 13/314,796; 13/314,749; and 13/314,842 have focused on
removing the olefinic compounds, and in particular dienes such as
butadiene or isoprene from a benzene feed stream or a benzene
stream exiting the styrene plant prior to directing the stream
through a nitrogen compound removal guard bed. In this manner, a
large portion of the dienes can be removed from the stream prior to
contacting the guard bed catalyst with the stream to restrict the
dienes from contacting the guard bed and poisoning the nitrogen
adsorbent. With this in mind, these applications propose contacting
the benzene or other aromatic stream with adsorbents and/or
catalysts including clay, acidic molecular sieves, and/or activated
carbon in order to remove at least a portion of the dienes or other
C2 to C20 olefin alkylating agent or a poly-alkyl aromatic
hydrocarbon transalkylating agents present in a recycle or a fresh
feed stream prior to contacting the stream with the nitrogen
removal adsorbent to restrict these components from shortening the
life of the nitrogen guard bed.
[0010] It is also generally known that feed streams to alkylation
reactors in an ethylbenzene plant may include water. Particularly,
a recycle benzene stream from a styrene monomer production zone has
been found to include relatively large amounts of water. Without
being bound by theory, it is believed that the H-Y acidic molecular
sieve typically used to adsorb the nitrogen compounds from the
stream favors water to a much greater extent than nitrogen
compounds. In this regard, where water is present in greater
amounts than the nitrogen compounds, significant adsorbent capacity
is taken up by water, shortening the cycle length or life of the
adsorbent. Further, it is believed that certain adsorbents, such as
the H-Y acidic molecular sieve used for nitrogen removal may
catalyze the polymerization of dienes. This can lead to the
blockage of accessible surface area of the adsorbent and coke
formation where the adsorbent is regenerated by carbon burn further
degrading the effectiveness and useful life of the adsorbent for
removing nitrogen components from the stream.
[0011] Increases in crude oil prices have created renewed interest
in utilizing available streams for recycle in petrochemical
processes. Thus, it is desirable to identify ways to utilize feeds
and recycle streams in an effective and economical manner for use
in aromatic conversion processes while avoiding the problems
associated with the presence of the contaminants in the feeds as
discussed above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a flow diagram of a hydrocarbon feed stream
treatment zone in accordance with various embodiments;
[0013] FIG. 2 is a flow diagram of an alkylation facility that
includes a hydrocarbon feed stream treatment zone in accordance
with various embodiments; and
[0014] FIG. 3 is a flow diagram of a styrene monomer facility in
accordance with various embodiments.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Hydrocarbon conversion processes, such alklylation and/or
transalkylation of a benzene feed stream to form ethylbenzene and
the dehydrogenation of the ethylbenzene stream to form a styrene
monomer stream are well known. Various aspects provided herein
provide methods and apparatus for treating a hydrocarbon feed
stream, including, for example, a recycle feed stream, to
hydrocarbon conversion processes, wherein water, one or more
nitrogen compounds, and one or more unsaturated aliphatic
hydrocarbon compounds are removed from the hydrocarbon feed stream.
The hydrocarbon feed stream includes an aromatic compound, water, a
nitrogen compound, and an unsaturated aliphatic compound. The
treated hydrocarbon feed stream has a lower water, nitrogen
compound, and unsaturated aliphatic hydrocarbon content relative to
the hydrocarbon feed stream.
[0016] In accordance with an aspect, the aromatic hydrocarbon
compound may be selected from the group consisting of benzene,
toluene, and naphthalene and substituted derivatives thereof, with
benzene and its derivatives being preferred aromatic compounds.
[0017] The aromatic compound may have one or more of the
substituents selected from the group consisting of alkyl groups
having from 1 to about 20 carbon atoms, hydroxyl groups, and alkoxy
groups whose alkyl group also contains from 1 up to 20 carbon
atoms. Where the substituent is an alkyl or alkoxy group, a phenyl
group can also be substituted on the alkyl chain.
[0018] Although unsubstituted and monosubstituted benzenes,
toluenes, and naphthalenes, are most often used, polysubstituted
aromatics also may be employed. Examples of suitable alkylatable
aromatic compounds in addition to those cited above may include
anthracene, phenanthrene, biphenyl, xylene, ethylbenzene,
propylbenzene, butylbenzene, pentylbenzene, hexylbenzene,
heptylbenzene, octylbenzene, etc.; phenol, cresol, anisole,
ethoxy-, propoxy-, butoxy-, pentoxy-, hexoxybenzene, and so forth.
Sources of benzene, toluene, xylene, and or other feed aromatics
include product streams from naphtha reforming units, aromatic
extraction units, recycle streams from styrene monomer production
units, and petrochemical complexes for the producing para-xylene
and other aromatics. However, the hydrocarbon feed stream includes
at least one aromatic hydrocarbon compounds. According to one
example, the concentration of the aromatic compound in the
hydrocarbon feed stream ranges from about 5 wt % to about 99.9 wt %
of the hydrocarbon feed. By another example, the hydrocarbon feed
stream comprises between about 50 wt % and about 99.9 wt %
aromatics, and may comprise between about 90 wt % and about 99.9 wt
% aromatics.
[0019] By one aspect, the hydrocarbon feed stream nitrogen compound
may include one or more organic nitrogen compounds. Organic
nitrogen compounds typically include a larger proportion of basic
nitrogen compounds such as indoles, pyridines, quinolines,
diethanol amine (DEA), morpholines including N-formyl-morpholine
(NFM) and N-methyl-pyrrolidone (NMP). Organic nitrogen compounds
may also include weakly basic nitriles, such as acetonitrile,
propionitrile, and acrylonitrile. Specific examples of nitrogen
compounds that may be found in the hydrocarbon feed stream include,
but are not limited to, nitriles, acetonitrile, and
propionitrile.
[0020] According to one aspect, the nitrogen compound in the
hydrocarbon feed stream may result from adding an inhibitor or a
retardant in an upstream process or downstream process where a
process stream is recycled back upstream. For ease of explanation,
inhibitors and retardants will collectively be referred to as
"inhibitors" from here forward. Adding various nitrogen compound
containing inhibitors to a stream during certain processes has been
found to inhibit polymerization of a component in the stream and/or
reduce corrosion of equipment within a processing unit. For
example, as illustrated in FIG. 3, which is addressed again further
below, an inhibitor may be added to a styrene monomer production
zone 205 of an ethylbenzene-styrene complex in order to inhibit
polymerization of a styrene monomer within a styrene stream during
separation of a styrene product from other components in the
styrene stream, in for example, separation zone 255. The inhibitor
may also act to reduce corrosion within the vessels used to carry
out these processes. In this example, when a benzene stream is
recycled from the styrene monomer production zone 205 to provide at
least a portion of a hydrocarbon feed stream comprising benzene,
the recycle benzene stream may contain residual nitrogen compounds
from the upstream addition of the inhibitor. The hydrocarbon feed
stream nitrogen compound may be in the same or a different form
than the inhibitor nitrogen compound, due to, for example, a
reaction or conversion of the inhibitor nitrogen compound.
[0021] Chemical compositions of proprietary inhibitors in
commercial use are not widely known, however, certain typical
characteristics of such inhibitors are generally understood. U.S.
Pat. No. 7,276,636, which is incorporated herein by reference,
provides a description of the use of inhibitors, general
characteristics of inhibitors, and examples of inhibitors that may
be used in commercial processes in Col. 3, line 41 through col. 4,
line 65. These inhibitors, as well as others, may introduce the
nitrogen compounds present in the hydrocarbon feed stream. Some
specific, non-limiting examples of nitrogen compounds that may be
found in inhibitors include dinitrophenols,
2-sec-butyl-4,6-dinitrophenol, dialkylhydroxylamines, and
nitroxides as well as those described in U.S. Pat. No.
7,276,636.
[0022] In one example, the hydrocarbon feed stream has a nitrogen
component content ranging from about 1 ppm-wt to about 10 ppm-wt.
In another example, the concentration of organic nitrogen compounds
in the hydrocarbon feed ranges from about 30 ppb-wt (parts per
billion by weight) to about 1 mole % of the hydrocarbon feed; the
concentration of organic nitrogen compounds may range from about 30
ppb-wt to about 100 ppm-wt (parts per million by weight) of the
hydrocarbon feed. In yet another example, the concentration of
weakly basic organic nitrogen compounds such as nitriles in the
hydrocarbon feed ranges from about 100 ppb-wt to about 100 ppm-wt
of the hydrocarbon feed.
[0023] According to one aspect, the hydrocarbon feed stream
comprises one or more unsaturated aliphatic compounds, including
unsaturated cyclic hydrocarbons and straight and branched chain
olefinic hydrocarbons (olefins) having one or more double bonds.
Thus, as used herein the terms "olefins" and "olefinic
hydrocarbons" include diolefin compounds. In an example, the
unsaturated aliphatic compound is an olefin compound, and the
unsaturated aliphatic compound may be a diolefin compound. In
another example, the unsaturated aliphatic compound is one or more
diolefin compounds having four, five, or six carbon atoms per
molecule, i.e. the unsaturated aliphatic compound may be selected
from the group of diolefins consisting of C4-C6 acyclic and cyclic
diolefins, and mixtures thereof. In yet another example, the
diolefin compound is selected from the group consisting of
butadienes, pentadienes, methylbutadienes, hexadienes,
methylpentadienes, dimethylbutadienes, acetylenes, cyclopentadiene,
alkylcyclopentadiene, cyclohexadiene and mixtures thereof.
[0024] In an example, the concentration of diolefin compounds in
the hydrocarbon feed ranges from about 30 ppb-wt to about 3000
ppm-wt of the hydrocarbon feed; and the concentration of diolefin
compounds may range from about 50 ppb-wt to about 2000 ppm-wt of
the hydrocarbon feed. The hydrocarbon feed stream may comprise
other olefins such as mono-olefins. Typically, the overall
concentration of all olefins in the hydrocarbon feed stream will be
no more than 1.0 wt-% olefins.
[0025] In accordance with one aspect, the hydrocarbon feed stream
contains water. In an example, the concentration of water in the
hydrocarbon feed ranges from about 10 to about 10,000 ppm-wt of the
hydrocarbon feed. In accordance with another example, the
concentration of water in the hydrocarbon feed ranges from about 10
to about 1,000 ppm-wt. The hydrocarbon feed stream may also contain
oxygenates in addition to water such as, for example, alcohols and
ketones that may be removed with the water components from the
hydrocarbon feed stream.
[0026] In an example, the aromatic compound comprises benzene, the
nitrogen compound comprises an organic nitrogen compound, and the
unsaturated aliphatic compound comprises an olefin compound. In
another example, the aromatic compound comprises benzene, the
nitrogen compound comprises an organic nitrogen compound, and the
unsaturated aliphatic compound comprises an olefin compound having
four to six carbon atoms per molecule. In another example, the
aromatic compound comprises benzene, the nitrogen compound
comprises an organic nitrogen compound, and the unsaturated
aliphatic compound comprises a diolefin compound.
[0027] Apparatus 2 and processes for treating a hydrocarbon feed
stream in accordance with various aspects are provided. Referring
to FIG. 1, an apparatus includes a feed stream treatment zone 4 for
removing one or more compounds from the feed stream. By one aspect,
a hydrocarbon feed stream is provided via line or conduit 5 to a
water removal zone 10. The water removal zone includes an inlet 15
in fluid communication with the line 5 for receiving the
hydrocarbon feed stream and an outlet 20. The water removal zone
removes at least a portion of the water from the hydrocarbon feed
stream to provide a reduced water content feed stream. By one
aspect, the water removal zone 10 includes a water selective
adsorbent that preferentially adsorbs water over one or more other
components in the hydrocarbon feed stream that contacts the
hydrocarbon feed stream as it flows through the water removal zone
10 to remove at least a portion of the water from the hydrocarbon
feed stream. The reduced water content hydrocarbon feed stream
having a lower concentration of water relative to the feed stream
entering the inlet 15 of the water removal zone, exits through the
outlet 20 of the water removal zone into a line 25 in fluid
communication with the outlet 20.
[0028] By one aspect, the feed stream treatment zone 4 also
includes a nitrogen removal zone 30, having a nitrogen removal zone
inlet 35 and a nitrogen removal zone outlet 40. The reduced water
feed stream is provided to the nitrogen removal zone 30 via the
line 25, which provides fluid communication between the water
removal zone outlet 20 and the nitrogen removal zone inlet 35. The
nitrogen removal zone 30 removes a nitrogen compound from the feed
stream to provide a reduced nitrogen feed stream that has a lower
nitrogen concentration than the reduced water feed stream entering
the nitrogen removal zone 30 via the inlet 35. By one aspect, the
nitrogen removal zone 30 includes a nitrogen selective adsorbent
that contacts the feed stream and preferentially adsorbs nitrogen
over one or more other components in the feed stream for removing
the nitrogen compound from the feed stream. A reduced nitrogen feed
stream exits the nitrogen removal zone 30 via the outlet 40.
[0029] The feed stream treatment zone 4 further includes an
unsaturated aliphatic compound removal zone 50 having an
unsaturated aliphatic compound removal zone inlet 55 and an
unsaturated aliphatic compound removal zone outlet 60. The feed to
the aliphatic compound removal zone 50, which has a reduced
concentration of both water and one or more nitrogen compounds, is
provided to the unsaturated aliphatic compound removal zone 50 via
the line 45, which provides fluid communication between the
nitrogen removal zone outlet 40 and the unsaturated aliphatic
compound removal zone inlet 55. The unsaturated aliphatic compound
removal zone 50 removes at least one unsaturated aliphatic compound
from the feed stream to provide a reduced unsaturated aliphatic
compound feed stream that has a lower concentration of the one or
more unsaturated aliphatic compounds than the feed stream entering
the unsaturated aliphatic removal zone 50 via the inlet 55. By one
aspect, the unsaturated aliphatic compound removal zone includes an
unsaturated aliphatic compound adsorbent that preferentially
adsorbs the unsaturated aliphatic compound over one or more other
components in the feed stream.
[0030] By one aspect, the feed stream treatment zone 4 includes all
three of the water removal zone 10, the nitrogen removal zone 30,
and the unsaturated aliphatic compound treatment zone 50. According
to one aspect, the water removal zone 10, the nitrogen removal zone
30, and the unsaturated aliphatic compound treatment zone 50 are
provided in series, such that the hydrocarbon feed stream is
treated by sequentially passing the hydrocarbon feed stream through
the water removal zone 10, the nitrogen removal zone 30, and the
unsaturated aliphatic compound treatment zone 50. By another
aspect, the hydrocarbon feed stream is sequentially contacted by a
water selective adsorbent to remove water from the stream; a
nitrogen selective adsorbent to remove nitrogen from the stream,
and a unsaturated aliphatic compound adsorbent to remove an
unsaturated aliphatic compound from the stream.
[0031] Turning to more of the particulars, the water removal zone
10 removes at least a portion of the water from the feed stream.
The water removal zone 10 may include a water selective adsorbent
that selectively adsorbs water over one or more other components in
the feed stream. It should be understood, however, that the water
selective adsorbent may also adsorb other components in the feed
stream, such as, for example, one or more nitrogen compounds from
the feed stream. Further, in accordance with other aspects, other
components may be provided in the water removal zone for removing
at least a portion of the water from the feed stream.
Alternatively, in accordance with other aspects, other apparatus
and methods may be provided for removing at least a portion of the
water from the hydrocarbon feed stream in the water removal zone
10. For example, trays may be provided for drying the hydrocarbon
feed stream as is known in the art. A drier may also be used to
remove a portion of the water in the water removal zone 10.
[0032] The water may be removed from the hydrocarbon stream by
various mechanisms such as adsorption, reaction, and reactive
adsorption with the adsorbent. By one aspect, a water selective
molecular sieve preferentially adsorbs water over an aromatic
compound in the hydrocarbon feed stream. By another aspect, the
water selective molecular sieve preferentially adsorbs water over
one or more nitrogen compounds and one or more unsaturated
aliphatic compounds in the hydrocarbon stream. In one approach, the
water selective molecular sieve includes a zeolite material. In one
example, the zeolite material may include Zeolite A, Zeolite X,
Zeolite Y or mixture of thereof. Examples of specific zeolites that
may be used include Zeolites 3A, 4A, 5A and 13X. Zeolites 3A and 4A
are preferred as they will not adsorb large amounts of nitrogen
compounds, unsaturated aliphatic compounds, benzene or other
aromatic hydrocarbons in the feed.
[0033] By one aspect, the water selective adsorbent may include a
zeolite with a pore diameter that is large enough to adsorb water
molecules, but small enough to restrict adsorption of most of the
nitrogen compounds and/or unsaturated aliphatic compounds from the
stream. Pore diameter refers to the average pore diameter of the
adsorbent as measured by gas adsorption methods, including N2
adsorption, and is provided in units of Angstroms. Dubinin-Astakhov
or Dubinin-Radushkevich equations may then be used to estimate
micropore volume and surface area, from which average pore diameter
can be calculated. In one example, the water selective adsorbent
may include a zeolite with a pore diameter of between about 2 .ANG.
and about 8 .ANG.. By another example, the water selective
adsorbent may include a zeolite with a pore diameter of between
about 2.5 .ANG. and about 6 .ANG.. In yet another example, the
water selective adsorbent may include a zeolite with a pore
diameter of between about 2.8 .ANG. and about 4.2 .ANG., and in one
example; the water selective adsorbent includes a zeolite with
about 3 .ANG.-4 .ANG. pore diameter.
[0034] By one aspect, the water removal zone 10 includes a water
removal device 11. In one approach, the water removal device
includes a water removal vessel 12 as illustrated in FIG. 1 for
holding the water selective adsorbent, such that the hydrocarbon
feed stream enters the water removal vessel 12 through the inlet 15
to contact the water selective adsorbent and exits through the
outlet 20. The inlet 15 and outlet 20 may be an inlet and outlet to
the vessel 12. Alternatively the water removal zone 10 may be
combined into a single vessel with one or both of the nitrogen
removal zone 30 and the unsaturated aliphatic compound removal zone
50. Internal structures or equipment within a single vessel may
separate the different zones. In this regard, the inlet and/or
outlet may be an inlet and/or outlet to or from a particular region
of a larger vessel that contains the water removal zone 10 and one
or more of the other zones. According to other aspects, the water
removal device 11 may include trays or a drier for removing a
portion of the water from the hydrocarbon stream as is generally
known in the art.
[0035] By one approach, as the hydrocarbon feed stream passes
through the water removal zone, it enters the water removal vessel
12 and contacts the water selective adsorbent under contacting
conditions, so that at least a portion of the water within the
hydrocarbon feed stream is removed by the water selective
adsorbent. In an example, the contacting temperature ranges from
about 10.degree. C. to about 300.degree. C. and the contacting
temperature may range from about 20.degree. C. to about 250.degree.
C. In another example, the contacting temperature ranges from about
25.degree. C. to about 225.degree. C.; and the contacting
temperature may range from about 50.degree. C. to about 125.degree.
C.
[0036] In one example, at least about 50% of the water is removed
from the hydrocarbon feed stream. In another example, between about
60% and about 99% of the water, and in yet another example between
about 80% and about 99% of the water is removed from the
hydrocarbon feed stream as it contacts the water selective
molecular sieve. According to one aspect, the feed stream includes
between about 10 and about 1000 ppm water. After the hydrocarbon
feed stream passes through the water removal zone 10 and contacts
the water selective adsorbent, the reduced water content feed
stream includes between about 0.1 and about 100 ppm water. By
another approach, after the hydrocarbon feed stream passes through
the water removal zone 10, the reduced water content feed stream
includes between about 0.1 and about 30 ppm water. By yet another
approach, the reduced water content feed stream includes less than
about 10 ppm water. By one aspect, the water selective adsorbent
removes substantially all of the water in the feed stream, by one
example above 95% of the water in the feed stream is removed. It
should be noted that according to various aspects, it may be
desirable that only a portion of the hydrocarbon feed stream may be
contacted with the water removal adsorbent in the water removal
zone 10 where not all of the water in the feed stream needs to be
removed. In this regard, the remainder of the feed stream may
bypass the water removal adsorbent or the water removal zone 10
entirely so that only a portion of the water is removed from the
hydrocarbon feed stream. The bypass stream may then rejoin the
treated stream.
[0037] In this manner, water is adsorbed by the water selective
adsorbent, while a large portion of the nitrogen compounds and
unsaturated aliphatic compounds in the hydrocarbon feed stream pass
downstream through the outlet 20 and through line 25 for further
treatment. In this manner, the water molecules which have been
identified to quickly deactivate basic adsorbents that are useful
for removing nitrogen compounds, are mostly removed from the
hydrocarbon feed stream by the time it exits the outlet 20 and is
passed downstream to the nitrogen removal zone 30 to reduce their
poisoning of the nitrogen selective adsorbent.
[0038] By various aspects, as described previously, after the feed
stream passes through the water removal zone 10 the reduced water
feed stream is passed to the nitrogen removal zone 30, which
removes at least a portion of one or more nitrogen compounds from
the feed stream. As discussed above, various methods are well known
in the art to remove nitrogen compounds from aromatic hydrocarbon
streams. See, for example, U.S. Pat. No. 7,205,448; U.S. Pat. No.
7,744,828; U.S. Pat. No. 6,297,417; each of which is herein
incorporated by reference in its entirety. In brief, the treated
hydrocarbon stream is introduced to the nitrogen removal zone which
includes at least one adsorbent effective to remove nitrogen. The
nitrogen compounds may be removed from the hydrocarbon stream by
various mechanisms such as adsorption, reaction, and reactive
adsorption with the adsorbent. By one aspect, the nitrogen removal
zone 30 may include a nitrogen selective adsorbent that
preferentially adsorbs nitrogen over one or more other components
in the feed stream. It should be understood, however, that the
nitrogen selective adsorbent may also adsorb other components in
the feed stream, such as, for example, water or one or more
unsaturated aliphatic compounds from the feed stream. Further, in
accordance with other aspects, other components may be provided in
the nitrogen removal zone in addition to, or instead of, the
nitrogen selective adsorbent for removing at least a portion of the
nitrogen from the feed stream
[0039] By one aspect, the nitrogen removal adsorbent may include an
acidic adsorbent. In this regard, suitable adsorbents include
acidic clays, resins, and zeolites. By one aspect, the nitrogen
removal zone may comprise two adsorbents such as an acidic clay or
resin adsorbent being located upstream of an acidic zeolite
adsorbent so the treated hydrocarbon stream contacts the clay or
resin adsorbent first to produce an intermediate stream which then
contacts the zeolite adsorbent.
[0040] Suitable acidic zeolites for use in a nitrogen removal zone
may include those having a high number of accessible sites that are
able to interact with nitrogen containing molecules. Acidic
zeolites suitable for removing nitrogen compounds in hydrocarbons
includes but not limited to zeolites BPH, EMT, Faujasite, LTL, BEA,
MAZ, MOR, MFI, MEI and mixtures thereof The ranges of silica to
alumina ratios depend on the specific structure of the zeolite
used, but may typically range from about 2 to about 40. The choice
of zeolites depends on the type and concentration of nitrogen
compounds and the degree of nitrogen removal desired. In general,
at least 50% of framework anion is balanced by proton and
preferably at least 70% of the framework anion is balanced by
proton.
[0041] It has been discovered that acidic zeolites, such as H-Y,
currently used to adsorb nitrogen compounds may favor water
adsorption to a much greater extent than nitrogen compounds. In
this regard, significant adsorbent capacity may be taken up by
water in the stream, shortening the cycle length of the adsorbent.
Acidic zeolites may also catalyze the polymerization of dienes,
leading to the blockage of accessible surface area and coking when
the adsorbent is regenerated by carbon burn. By removing at least a
portion of the water upstream in accordance with various aspects,
some of these problems may be reduced.
[0042] By another aspect, the nitrogen selective adsorbent may
include a preferred basic zeolite in order to decrease the extent
of polymerization of dienes or other unsaturated aliphatic
compounds within the stream. The basic zeolite used in the nitrogen
removal zone 30, in accordance with various aspects, is less
susceptible to deactivation by dienes than an acidic adsorbent, so
that the hydrocarbon feed stream can be treated for nitrogen
removal in nitrogen removal zone 30 in the presence of dienes in
the stream without quickly deactivating the zeolite, increasing the
amount of time between change-out or regeneration of the nitrogen
selective adsorbent.
[0043] In this regard, the nitrogen selective adsorbent may include
a basic zeolite for contacting the hydrocarbon feed stream and
removing a nitrogen compound therefrom as is generally known in the
art. According to one aspect, the nitrogen selective adsorbent may
include a basic zeolite material, for example like those described
in U.S. Pat. No. 5,271,835, which is incorporated by reference
herein. The particular zeolite may be selected to have a high
cation density of above about 50 in one example, between about 60
and about 99 in another example, and between about 80 and 99 in yet
another example. By one aspect, the nitrogen selective adsorbent
may include a zeolite having a silicon to aluminum ratio (Si/Al) of
between about 1 and about 12. By another aspect, the nitrogen
selective adsorbent may have a Si/Al ratio of between about 1.2 and
6.0. The nitrogen selective adsorbents according to this aspect may
include zeolite LTA, BPH, EMT, Faujasite, LTL, MOR and the mixture
of thereof, with at least 50% of framework charges balanced by
alkali and/or alkali earth cations.
[0044] The nitrogen removal zone 30 may include a nitrogen removal
vessel 32 as illustrated in FIG. 1 for holding the nitrogen
selective adsorbent, such that the hydrocarbon feed stream enters
the nitrogen removal vessel 32 through the inlet 35 to contact the
nitrogen selective adsorbent and exit through the outlet 40. In
this approach, the inlet 35 and outlet 40 may be an inlet and
outlet to the vessel 32. The nitrogen removal zone 30 may also be
combined into a single vessel with one or both of the water removal
zone 10 and the unsaturated aliphatic compound removal zone 50.
Internal structures or equipment within a single vessel may
separate the different zones. In this regard, the inlet and/or
outlet may be an inlet and/or outlet to or from a particular region
of a larger vessel that contains the nitrogen removal zone 30 and
one or more of the other zones.
[0045] By one aspect, as the hydrocarbon feed stream passes through
the nitrogen removal zone 30, it contacts the nitrogen selective
adsorbent under contacting conditions, so that at least a portion
of one or more nitrogen compounds within the hydrocarbon feed
stream is removed by the nitrogen selective adsorbent. In an
example, the contacting temperature ranges from about 10.degree. C.
to about 300.degree. C. and the contacting temperature may range
from about 20.degree. C. to about 125.degree. C. In another
example, the contacting temperature ranges from about 25.degree. C.
to about 90.degree. C.
[0046] In one example, at least about 50% of the nitrogen is
removed from the hydrocarbon feed stream, as measured, for example
by a nitrogen chemiluminescence method, ASTM D4629. In another
example, between about 70% and about 99.99% of the nitrogen is
removed from the hydrocarbon feed stream as it contacts the
nitrogen selective molecular sieve, and in another example between
about 90% and about 99.99% of the nitrogen is removed. According to
one aspect, the hydrocarbon feed stream to the nitrogen removal
zone 30 includes between about 0.03 and about 10 ppm nitrogen.
[0047] By one aspect, where water is removed from the feed stream
upstream of the nitrogen removal zone, the breakthrough time before
nitrogen reaches detectable levels in an effluent stream generated
by the nitrogen removal zone 30 is increased. In one example, the
breakthough time is at least about 10 hours. In another example,
the breakthrough time is at least about 25 hours. In yet another
example, the breakthrough time is at least about 50 hours. By
another aspect, the nitrogen adsorption at breakthrough of the
nitrogen removal adsorbent is above about 50% in one example, above
about 75% in another example, and above about 80% in yet another
example.
[0048] By another aspect, the feed stream entering the nitrogen
removal zone includes at least one unsaturated aliphatic compound.
However, it has been identified that by selecting a nitrogen
removal adsorbent as discussed above, including a basic adsorbent
according to one aspect, the presence of the aliphatic compound in
the feed stream does not largely affect the adsorption performance
or life of the nitrogen selective adsorbent. In one example, the
feed stream entering the nitrogen removal zone 30 includes at least
about 100 ppm-wt of unsaturated aliphatic compounds. In another
example, the feed stream entering the nitrogen removal zone 30
includes between about 100 and about 3000 ppm-wt of unsaturated
aliphatic compounds. In one example, the unsaturated aliphatic
compound is a diene. In one example, the breakthrough time of the
adsorbent where the feed stream includes at least about 100 ppm-wt
of unsaturated aliphatic compounds in one example and at least
about 400 ppm-wt of unsaturated aliphatic compounds in another
example decreases by less than 15% in one example, by less than 10%
in another example, and by less than 5% in yet another example,
when compared to the breakthrough time of the same adsorbent where
less than 1 ppm-wt of the unsaturated aliphatic compound is present
in the feed stream. The adsorption of the nitrogen selective
adsorbent at breakthrough decreases by less than 0.2% in one
example, by less than 0.1% in another example, and by less than
0.05% in yet another example when compared to the adsorption at
breakthrough of the same adsorbent where less than 1 ppm-wt of the
unsaturated aliphatic compound is present in the feed.
[0049] In accordance with various aspects, the treatment zone 4
includes an unsaturated aliphatic compound removal zone 50 for
removing or converting at least one unsaturated aliphatic compound
from the hydrocarbon feed stream. The unsaturated aliphatic
compound removal zone 50 may include an unsaturated aliphatic
compound removal material that removes at least a portion of the
unsaturated aliphatic compounds from the stream or reacts with the
unsaturated aliphatic compounds to convert them into other
compounds. By one aspect the unsaturated aliphatic compound removal
material is an unsaturated aliphatic compound adsorbent that
adsorbs at least one unsaturated aliphatic compound from the feed
stream. By one aspect, the unsaturated aliphatic compound adsorbent
adsorbs an unsaturated aliphatic compound in the feed stream but
does not substantially adsorb an aromatic compound in the
hydrocarbon feed stream.
[0050] Alternatively, according to various aspects, the unsaturated
aliphatic compound removal material may include an unsaturated
aliphatic compound catalyst that catalyzes an alkylation reaction
in which one or more unsaturated aliphatic compounds react with
aromatics in the feed stream to form one or more alkylaromatics. In
this regard, the unsaturated aliphatic compound catalyst may
include an acidic catalyst, which may include, but is not limited
to acidic clay, acidic zeolite and sulfate supported metal oxides
at a combination of temperatures and pressures under which the
alkylation reaction operates in liquid or partial liquid phase
conditions. For example, where the feed stream includes diolefins,
the unsaturated aliphatic compound catalyst may catalyze an
alkylation reaction of the diolefin. More particularly, benzene
within the feed stream may alkylate the diolefin and add benzene to
the double bond of the diolefin. In one example, the alkylation
reaction forms an alkylbenzene, and may form diphenylbenzene.
[0051] According to various aspects, the unsaturated aliphatic
compound removal material may act as both an adsorbent and a
catalyst such that a portion of the unsaturated aliphatic compound
in the stream are removed by adsorption while another portion of
the unsaturated aliphatic compound in the stream are reacted with
aromatics in the stream by contacting the unsaturated aliphatic
compound removal material to form one or more alkylaromatics.
[0052] By one aspect, the unsaturated aliphatic compound removal
material includes clay and may include acidified clay. Suitable
clays include, but are not limited to, beidellite, hectorite,
laponite, montmorillonite, nontonite, saponite, bentonite, and
mixtures thereof. In one form, the clay adsorbent includes an acid
activated bentonite and/or montmorillonite clay.
[0053] Advantageously, by one aspect, in removing nitrogen
compounds from the feed stream before it enters the unsaturated
aliphatic compound removal zone, nitrogen does not poison the
unsaturated aliphatic compound removal material, so that the life
of the material is extended before requiring change-out or
regeneration.
[0054] The hydrocarbon feed stream to be treated is contacted with
the unsaturated aliphatic removal material at contacting conditions
to remove or react one or more unsaturated aliphatic compounds and
produce a hydrocarbon stream with a reduced unsaturated aliphatic
compound concentration relative to the hydrocarbon feed stream
entering the inlet 55 of the unsaturated aliphatic compound removal
zone 50. The unsaturated aliphatic compounds may be removed from
the hydrocarbon stream by various mechanisms such as adsorption,
reaction, and reactive adsorption with the adsorbent. The treated
hydrocarbon stream has a lower unsaturated aliphatic compound
concentration relative to the unsaturated aliphatic compound
content of the hydrocarbon feed stream.
[0055] The unsaturated aliphatic compound removal zone 50 may
include an unsaturated aliphatic compound removal vessel 52 as
illustrated in FIG. 1 for holding the unsaturated aliphatic
compound removal material, such that the hydrocarbon feed stream
enters the unsaturated aliphatic compound removal vessel 52 through
the inlet 55 to contact the unsaturated aliphatic compound removal
material and exit through the outlet 60. The inlet 55 and outlet 60
may be an inlet and outlet to and from the vessel 52. The
unsaturated aliphatic compound removal zone 50 may also be combined
into a single vessel with one or both of the water removal zone 10
and the nitrogen removal zone 30. Internal structures or equipment
within a single vessel may separate the different zones. In this
regard, the inlet and/or outlet 55 and 60 may be an inlet and/or
outlet to or from a particular region of a larger vessel that
contains the nitrogen removal zone 30 and one or more of the other
zones.
[0056] The contacting conditions in one example include a
temperature of at least about 50.degree. C. In another example, the
contacting temperature ranges from about 50.degree. C. to about
300.degree. C. In yet another example, the contacting temperature
ranges from about 75.degree. C. to about 250.degree. C.
[0057] Bromine Index is commonly used to assess the unsaturated
aliphatic compound content, including olefins and diolefins, of
hydrocarbon mixtures. (It should be noted that the terms
"diolefins" and "dienes" are used interchangeably herein) In one
example, the unsaturated aliphatic compound removal zone 50 reduces
the diolefin concentration in the hydrocarbon feed stream such that
Bromine Index is reduced by at least 50%. The Bromine Index is
reduced by at least about 70% in another example; at least about
90% in another example, and at least about 95 wt % in yet another
example. As used herein the Bromine Index of the hydrocarbon
streams or mixtures is determined using method UOP304. Unless
otherwise noted, the analytical methods used herein such as UOP304
are available from ASTM International, 100 Barr Harbor Drive, West
Conshohocken, Pa., USA.
[0058] Turning to FIG. 2, by one aspect, the hydrocarbon stream
treatment zone 4 is provided for treating a benzene feed stream to
an alkylation zone 110. According to various aspects, the feed
stream includes benzene, water, a nitrogen compound, and an
unsaturated aliphatic compound as mentioned previously. After the
benzene containing feed stream is treated in the hydrocarbon
treatment zone 4 to remove at least a portion of water, a nitrogen
compound, and an unsaturated aliphatic compound as described above
with regard to FIG. 1, the treated feed stream is passed along
conduit or line 105 to the alkylation zone 110. By one aspect, FIG.
2 illustrates that the alkylation zone 110 includes both an
alkylation reactor 115 and a transalkylation reactor 120. However,
the alkylation zone 110 may not include either the alkylation
reactor 115 or the transalkylation reactor 120 and may include more
than one alkylation reactor 115 and/or transalkylation reactor 120.
FIG. 2 illustrates that the treated hydrocarbon feed stream is
combined with another feed stream and passed into the alkylation
reactor 115. However, it should be understood that the treated
hydrocarbon feed stream can be combined with one or more other
streams to pass into the alkylation reactor 115 or the
transalkylation reactor 120 or be passed directly into the
alkylation reactor 115 or transalkylation reactor 120.
[0059] In one aspect, the treated hydrocarbon stream is passed via
line 105 to one or both of the alkylation reactor 115 and
transalkylation reactor 120. Another feed stream 125 may be
introduced to the alkylation zone 110 and combined with the treated
hydrocarbon feed stream or passed separately to one or both of the
alkylation reactor 115 and/or transalkylation reactor 120. In
addition, or alternatively, one or more additional streams may be
passed to the alkylation zone 110. An alkylating agent may be
introduced into an alkylation reactor 115 and contacted with the
treated hydrocarbon stream and an alkylation catalyst to produce an
alkylated benzene product which is sent downstream via line 135.
For example, ethylene may be introduced through line 130 to the
alkylation reactor 115 to contact the alkylation catalyst in the
presence of a treated benzene feed stream to produce an
ethylbenzene stream.
[0060] In the alkylation of an aromatics alkylation substrate by an
olefinic alkylating agent as catalyzed by an acidic catalyst, the
olefins may contain from 2 up to at least 20 carbon atoms, and may
be branched or linear olefins, either terminal or internal olefins.
Thus, the specific nature of the olefin is not particularly
important. Among the lower olefins, ethylene and propylene are the
most important representatives. An olefinic feed stream may be
introduced via line 130 and may include for example an alkylating
agent of ethylene and/or propylene. Alkylating agents may also be
provided by alkyl constituents of a polyalkylbenzene in a
transalkylation reactor 120. Diethylbenzene, triethylbenzene and
diisopropylbenzene are prominent examples of polyalkylbenzenes that
can provide such alkylating agents.
[0061] A wide variety of catalysts can be used in the alkylation
zone 110. Catalysts have typically included those that do not
suffer deleterious effects from the presence of water. In one
approach, a substantial quantity of water may be tolerated or
desired in the presence of the alkylation catalyst. However,
according to various aspects, other catalysts that are not as water
tolerant may be used since at least a portion of the water in the
hydrocarbon feed stream may be removed in the water removal zone 10
as discussed previously. The preferred catalyst for use in this
invention is a zeolitic catalyst. The catalyst of this invention
will usually be used in combination with a refractory inorganic
oxide binder. Preferred binders are alumina or silica. Suitable
zeolites include zeolite beta described in U.S. Pat. No. 5,723,710,
ZSM-5, PSH-3, MCM-22, MCM-36, MCM-49, MCM-56, type Y zeolite, and
UZM-8, which includes the aluminosilicate and substituted
aluminosilicate zeolites described in U.S. Pat. No. 6,756,030 and
the modified UZM-8 zeolites, such as, UZM-8HS which are described
in U.S. Pat. No. 7,091,390. Each of U.S. Pat. No. 6,756,030 and
U.S. Pat. No. 7,091,390 is herein incorporated by reference in its
entirety.
[0062] The basic configuration of a catalytic aromatic alkylation
zone is known in the art. The feed aromatic alkylation substrate
and the feed olefin alkylating agent are preheated and charged to
generally from one to four reactors in series. Suitable cooling
means may be provided between reactors to compensate for the net
exothermic heat of reaction in each of the reactors. Suitable means
may be provided upstream of or with each reactor to charge
additional feed aromatic, feed olefin, or other streams (e.g.,
effluent of a reactor, or a stream containing one or more
polyalkylbenzenes) to any reactor in the alkylation zone. Each
alkylation reactor 115 may contain one or more alkylation catalyst
beds. The invention encompasses dual zone aromatic alkylation
processes such as those as described in U.S. Pat. No. 7,420,098
which is herein incorporated by reference in its entirety.
[0063] The particular conditions under which the alkylation
reaction is conducted depends upon the aromatic compound and the
olefin used. One condition is that the reaction be conducted under
at least partial liquid phase conditions. Therefore, the reaction
pressure is adjusted to maintain the olefin at least partially
dissolved in the liquid phase. For higher olefins the reaction may
be conducted at autogenous pressure. The alkylation conditions
usually include a pressure in the range between about 1379 kPa(g)
and 6985 kPa(g). The alkylation of the aromatic compounds with the
olefins in the C2 to C20 range can be carried out at a temperature
of about 60.degree. C. to about 400.degree. C. In a continuous
process this time can vary considerably, but is usually from about
0.1 to about 8 hr.sup.-1 weight hourly space velocity (WHSV) with
respect to the olefin. In particular, the alkylation of benzene
with ethylene can be carried out at temperatures of about
150.degree. C. to about 260.degree. C. and the alkylation of
benzene with propylene at a temperature of about 90.degree. C. to
about 200.degree. C. The ratio of alkylatable aromatic compound to
olefin used in the instant process will depend upon the degree of
monoalkylation desired as well as the relative costs of the
aromatic and olefinic components of the reaction mixture. For
alkylation of benzene by propylene, the benzene-to-olefin molar
ratio may be as low as about 0.1 and as high as about 10. Where
benzene is alkylated with ethylene a benzene-to-olefin ratio may be
between about 0.1 and 10.
[0064] The alkylation reaction zone will often provide a wide
variety of secondary by-products. For example, in the alkylation of
benzene with ethylene to produce ethylbenzene, the reaction zone
can also produce di- and triethylbenzene in addition to other
ethylene condensation products. Another non-limiting exemplary
reaction that is contemplated herein includes the alkylation of
benzene with propylene to produce cumene. In this type of reaction,
the reaction zone can produce di- and triisopropylbenzene in
addition to still more condensation products. As is well known in
the art, these polyalkylated aromatics may contact additional
aromatic substrate in a transalkylation zone to produce additional
monoalkylated product. See e.g. U.S. Pat. No. 7,622,622 and U.S.
Pat. No. 7,268,267, which are incorporated by reference herein. It
should be noted that transalkylation reactions may occur in an
alkylation reaction zone and alkylation reactions occur in a
transalkylation reaction zone. Thus, as used herein alkylation zone
110 refers to a zone in which one or both of alkylation and
transalkylation reactions occur. In an embodiment, the alkylated
benzene product comprises at least one of ethylbenzene and
cumene.
[0065] An alkylated aromatic separation zone may also be provided
for separating a concentrated alkylated aromatic stream from the
alkylated aromatic stream produced by the alkylation zone 110. The
alkylated aromatic separation zone may include one or more
distillation or fractionation columns or other separation apparatus
as known in the art for separating a concentrated alkylated
aromatic stream from other components in the alkylated aromatic
stream. I should be noted that the term "concentrated" as used
herein does not mean the resultant stream is free from other
components, but rather that it has a higher concentration of the
desired product than the stream fed into the separation apparatus.
For example, as illustrated in FIG. 2, where the alkylation zone
produces an ethylbenzene stream via line 135, the alkylated
aromatic separation zone may include an ethylbenzene separation
zone 150 for separating a concentrated ethylbenzene stream from a
stream including benzene, poly-ethylbenzene, and other components.
A benzene fractionation column 155 may be in fluid communication
with an outlet of the alkylation zone 110 and configured to receive
the ethylbenzene stream via line 135 from the alkylation zone
outlet and to separate benzene from the feed stream, which exits
the benzene fractionation column through an alkylation benzene
recycle stream via line 160. The alkylation benzene recycle stream
may be passed back to the alkylation zone 110 as additional benzene
feed. An ethylbenzene fractionation column 165 may be in fluid
communication with the benzene fractionation column 155 via line
170 and may be provided to receive the benzene reduced ethylbenzene
stream via line 170 to produce a concentrated ethylbenzene stream
via fractionation. The ethylbenzene may provide a product stream or
it may be transferred downstream via line 175. A poly-ethylbenzene
fractionation column 180 may be provided to receive the
ethylbenzene depleted stream via line 185 and to separate a
concentrated poly-ethylbenzene stream, which may be recycled back
to a transalkylation reactor 120 via line 190 as a feed to the
transalkylation reactor to produce additional ethylbenzene.
[0066] According to an aspect, the hydrocarbon stream may include a
benzene recycle stream provided from a styrene monomer production
zone. Turning to FIG. 3, an example of a styrene production zone
205 of a styrene production plant is illustrated. An ethylbenzene
feed stream may be provided to the styrene monomer production zone
205 via line 210. The ethylbenzene feed stream may be provided via
line 210 by forming the ethylbenzene stream by alkylation in the
alkylation zone 110 and separation of the alkylation zone
ethylbenzene stream by the separation zone 150 via line 175 to
provide a concentrated ethylbenzene stream, which may include one
or more other components, including benzene, as described above
with regard to FIG. 2, or it may be provided by another source. In
the styrene monomer production zone 205, the ethylbenzene stream is
passed to a dehydrogenation zone 220 via line 215, where a
dehydrogenation reaction occurs to produce a styrene stream via
line 215.
[0067] The general layout and operation of styrene monomer
production plants is well known, and one process flow is described
and shown generally in U.S. Pat. No. 4,479,025, which is
incorporated by reference herein. In an exemplary system, the
dehydrogenation zone 220 includes one or more dehydrogenation
reactors with a dehydrogenation catalyst for contacting the
ethylbenzene stream and converting a portion of the ethylbenzene to
styrene to form a mixed styrene stream, as is generally known in
the art. The dehydrogenation zone 220 may also include steam
sources and/or generators 225 and a superheater 230 for heating the
steam, which is combined with the ethylbenzene feed stream and
passed to the dehydrogenation zone 220. In the dehydrogenation zone
220, the ethylbenzene in the stream is contacted with the
dehydrogenation catalyst under dehydrogenation conditions to
produce a stream that includes unreacted ethylbenzene, styrene,
benzene, toluene, steam, and hydrogen. The mixed styrene stream is
cooled via heat exchanger 235 and sent to condenser 240 to produce
a mixed phase stream. The stream is separated in the mixed phase
separator into a liquid phase including water with dissolved
hydrocarbons, a vapor phase, and a hydrocarbon liquid phase. The
hydrocarbon liquid phase stream may include styrene, ethylbenzene,
toluene, benzene, and other components, and is passed via line 250
to a separation zone 255.
[0068] As illustrated in FIG. 3, the separation zone may include an
ethylbenzene/styrene splitter 255 for separating an ethylbenzene
stream, including benzene and toluene, via line 260 from a styrene
concentrated stream via line 265. The concentrated styrene stream
may be passed via line 265 to a styrene finishing column 270 to
produce a styrene product via line 275. The ethylbenzene stream may
be passed via line 260 to an ethylbenzene recycle column 280. The
ethylbenzene recycle column separates an ethylbenzene recycle
stream and a stream including lighter hydrocarbon components,
including benzene, which is passed via line 285 to benzene column
290. The benzene column 290 separates a benzene recycle stream that
is exits the benzene column 290 via line 295.
[0069] According to one aspect, an inhibitor is added to the
hydrocarbon liquid phase stream as is generally known in the art,
in order to restrict the styrene from polymerizing and/or causing
corrosion of the separation equipment. As described previously, the
inhibitor may include one or more nitrogen compounds generally
known to restrict polymerization of styrene and/or corrosion of
equipment. Potential inhibitors are described above. As illustrated
in FIG. 3. the inhibitor may be introduced from an inhibitor source
292 into the ethylbenzene/styrene splitter 255 via line 293.
[0070] Referring back to FIG. 2, the benzene recycle stream may be
passed via line 300 back to the alkylation zone 110 for alkylation
of the benzene stream in the presence of ethylene to form
additional ethylbenzene. Due to the introduction of the inhibitor
and steam during the dehydrogenation and separation processes in
the styrene monomer production zone 205 described previously with
regard to FIG. 3, the recycle benzene stream will typically include
water, one or more nitrogen containing compounds, and one or more
unsaturated aliphatic compounds as described above. In this regard,
the benzene recycle stream may be passed via line 300 to the
hydrocarbon treatment zone 4 described previously with regard to
FIGS. 1 and 2, to remove at least a portion of these components
prior to the benzene recycle stream entering the alkylation zone
110, where these components could potentially cause deactivation of
the alkylation or transalkylation catalyst or otherwise shorten the
life of the catalyst.
[0071] The exemplary ethylbenzene production plant and styrene
monomer production plant illustrated in FIGS. 2 and 3 respectively
are intended to illustrate one possible process flow, and are not
intended to limit the scope of the invention which may be practiced
in other process flows.
[0072] By one aspect, a method is provided for treating a
hydrocarbon feed stream including an aromatic compound, a nitrogen
compound, an unsaturated aliphatic compound, and water as described
previously. The method includes removing at least a portion of the
water from the hydrocarbon feed stream. By one aspect, the method
includes contacting the hydrocarbon stream with a water selective
adsorbent at contacting conditions to remove the water from the
feed stream. The method further includes contacting the hydrocarbon
stream with a nitrogen selective adsorbent at contacting conditions
to remove a nitrogen compound from the feed stream. The method also
includes contacting the hydrocarbon stream with an unsaturated
aliphatic compound removal material to remove an unsaturated
aliphatic compound from the hydrocarbon stream to produce a treated
hydrocarbon stream. The method according to this aspect may include
contacting the hydrocarbon stream with an unsaturated aliphatic
compound adsorbent, an unsaturated aliphatic compound catalyst, or
both.
[0073] By one aspect, the above steps are carried out sequentially.
It has been found that by contacting the hydrocarbon feed stream
with particular adsorbents and/or materials as described
previously, in this order, the contaminants can be removed from the
hydrocarbon feed stream so that it can provide a useful feed to an
alkylation zone without deactivating the alkylation and/or
transalkylation catalysts. Surprisingly, it has also been
identified, that the selection of particular adsorbent and/or
catalyst materials, and the order of contacting the hydrocarbon
stream with the adsorbents, removes compounds from the feed stream
that can reduce the life of the downstream adsorbents. Namely, by
first removing water from the feed stream, for example by first
contacting the hydrocarbon feed stream with a water selective
adsorbent, at least a portion of water is removed from the feed
stream so that the water is not substantially shorten the lifecycle
of the nitrogen selective adsorbent and/or the unsaturated
aliphatic compound removal material. By next contacting the
hydrocarbon feed stream with a nitrogen selective adsorbent, at
least a portion of the nitrogen compounds are next removed from the
hydrocarbon feed stream so that these nitrogen compounds do not as
quickly deactivate the unsaturated aliphatic compound removal
material. This can increase the amount of time that the process may
proceed before these downstream adsorbents and/or catalysts must be
changed-out or regenerated.
[0074] The above description and examples are intended to be
illustrative of the invention without limiting its scope. While
there have been illustrated and described particular embodiments of
the present invention, it will be appreciated that numerous changes
and modifications will occur to those skilled in the art, and it is
intended in the appended claims to cover all those changes and
modifications which fall within the true spirit and scope of the
present invention.
EXAMPLE 1
[0075] For each test, a basic zeolitic adsorbent for removing
nitrogen compounds from a feed stream included a commercially
available 13X-HP adsorbent. Prior to each test, the adsorbent was
pre-dried at 550.degree. F. for 4 hours in flowing nitrogen.
EXAMPLE 2
[0076] For Examples 3 and 4, 18.21 g of 8.times.14 mesh 13X-HP
beads were loaded into the isothermal zone of a 5/8'' diameter
reactor. The reactor was kept at a constant temperature of
40.degree. C. and pure benzene was flowed through the reactor at 90
g/hr to pressurize the system up to 550 psig. Once the system
reached 550 psig, feed was introduced at 90 g/hr and the reactor
effluent was analyzed via gas chromatography.
[0077] Two different samples of a commercial benzene recycle stream
(>99 wt % benzene) containing different amounts of one or more
of nitrogen compounds and dienes were used to evaluate the
effectiveness of the 13X-HP adsorbent to remove the nitrogen
compounds as described below. The analysis of the two example feeds
is reported in Table 1 with the analysis of the effluent or product
from each test. The nitrogen compound content was determined by gas
chromatography.
EXAMPLE 3
[0078] As an illustrative example, a benzene feed stream sample
containing 60 wt-ppm acetonitrile was used in the test according to
Example 1. The feed stream according to Example 2 had a dew point
of -40 C and a dienes level of 1000 wt-ppm.
EXAMPLE 4
[0079] As an illustrative example, a benzene feed stream (>99
wt-% benzene) sample containing 66 wt-ppm Acetonitrile and 904
wt-ppm Isoprene was used in the test according to Example 1 to
determine the effect that the diene isoprene has on the performance
of the 13X-HP. The feed stream according to Example 2 had a dew
point of -40 C.
TABLE-US-00001 TABLE 1 Feed Rate Temperature Breakthrough Nitrogen
Ads. @ Example Adsorbent Feed (g/hr) (.degree. C.) (hours)
Breakthrough 3 LR-13X 60 wt-ppm 90 40 77 0.859% Acetonitrile 4
LR-13X 904 wt-ppm 90 40 ACN-74 0.826% Isoprene ISO-6 66 wt-ppm
Acetonitrile
EXAMPLE 5
[0080] In an illustrative example, a 400 ml solution of
acetonitrile in benzene was prepared by adding acetonitrile and
benzene to a 500 mL beaker. Acetonitrile was added to the solution
at a concentration of 161 ppm by weight, or equivalently 55 ppmw
nitrogen. Next, 0.96 grams of activated 13X-HP adsorbent was added
to the beaker. A chemiluminescence analysis was performed by ASTM
method D4629 to verify the initial concentration of acetonitrile.
The beaker was then sealed and shaken for four hours. The
chemiluminescence analysis was repeated to determine the amount of
nitrogen present after shaking, and the amount of nitrogen adsorbed
by the 13X-HP. The results are shown below in Table 2.
EXAMPLE 6
[0081] In a comparative example, 400 ml of a solution of
acetonitrile, benzene, and water was prepared by adding
acetonitrile, water, and benzene to a 500 mL beaker. Acetonitrile
was added to the solution at a concentration of 161 ppm by weight,
or equivalently 55 ppmw of nitrogen. In addition, 168.8 .mu.L of
water (501 ppmw) was added to the solution. Next, 1.00 grams of
activated 13X-HP adsorbent was added to the beaker. A
chemiluminescence analysis was performed by ASTM method D4629 to
determine the initial concentration of acetonitrile in the
solution. The beaker was then sealed and shaken for four hours. The
chemiluminescence analysis was repeated to determine the amount of
nitrogen present after shaking. The results are shown below in
Table 2.
TABLE-US-00002 TABLE 2 Nitrogen Nitrogen in in Solution Solution
Before After Nitrogen Shaking Shaking on Example Adsorbent Solution
(wt-ppm) (wt-ppm) Adsorbent 5 LR-13X 161 ppmw 55 wt-ppm 38 wt-ppm
0.60 wt-% Acetonitrile in Benzene 6 LR-13X 161 ppmw 55 wt-ppm 48
wt-ppm 0.24 wt-% Acetonitrile 501 ppmw water in Benzene
* * * * *